AKRON—Marketers of tire repair materials are spreading the word to their customers about the latest recommendations that may change how some dealers repair shoulder injuries on commercial tires.
The Tread Rubber and Tire Repair Materials Manufacturers' Group (TRMG) introduced its Reinforced Shoulder Repair (RSR) recommendation during the Specialty Equipment Market Association Show last November to re-em-phasize the proper way to set the patch on a shoulder puncture up to 3/8-inch in size.
“The industry has experienced repair unit failures specific to injuries in the shoulder area of tires because the incorrect repair unit is being utilized. Repair unit construction design normally allows for 50 percent of the repair unit to be shifted off-center to accommodate full injury security,” according to the TRMG guideline.
“When the anchor portion of the repair unit, 25 percent on each end of the repair body, ends in a high-flex portion of the tire, the additional stress on the repair body structure can result in repair cord breakout or bonding failure.”
“So we decided it's time to reintroduce or re-emphasize the fact there are certain areas of the tire that you have to be aware of shear energy and the flexing that takes place, and that it's better, or more permanent, if you put the placement so that the patch ends don't end in a high-flex area of the tire,” said Joe Casebere, vice president of sales and marketing for Rema Tip Top North America, who was instrumental in composing the document.
“The RSR was just re-emphasizing the fact that patch placement in a tire is important. There are different physics that take place as the tire rotates that need to be accommodated with this additional stuff you're putting in there.”
The RSR uses the same basic procedures for regular puncture repairs, but with some differences in repair unit size and placement.
The TRMG guidelines include:
• Avoid ending repair unit reinforcement in the tire's flex zone;
• Keep prepared damage within guide lines on a template; and
• Use the “blue triangle” symbol on the tire's sidewall nearest the RSR injury to indicate that a repair is installed, in case an inflated bulge appears on the tire at the repair.
The recommendation provides the option of offsetting the patch over the repair—as long as 50-percent covers the injury—in order to avoid the flex zone. The offset recommendation alters the industry's radial age-old Center Over Injury (COI) philosophy.
“The center-over-injury didn't help our industry because everybody assumed that you had to center the patch over the injury and that's just not the case,” Mr. Casebere told Tire Business.
“There's 50 percent of that patch that can be moved or shifted in order to accommodate the fact that you want that patch body in a stable area of the tire or at least the ends.... If you follow the RSR recommendations, yes you're going to use a larger repair unit, but you're going to have the ends in an area that is not going to have any influence on breaking what you're adding.”
RSR “is re-emphasizing the fact that you need to be aware that within that casing, because of the way they are built and because of what we put them through—with cornering, with braking and with curbing and all those things—that different parts of the tire react differently. So if we're adding additional material to that tire, we need to be cognizant of the fact that there is a right way and a wrong way to place things and that the success that you have is determined by your placement.”
The tire shoulder wasn't an issue until tire makers began changing compounds and building up the thickness of the shoulder area, Mr. Casebere noted. “Even passenger tires have got one or two additional compounds in that transitional area to try and absorb some of that energy that takes place as you go from a stiff portion of the tire to a flexible side of the tire, otherwise you have the belt packages separating from the casing body ply....
“With the engineering that took place over the years with better and better belt packages and thinner and thinner sidewalls, it became more of an issue with the center-over-injury type repair,” he said. “And what happened 25 years ago was the patch line in general expanded because it seemed like, for every type of injury in every place in a tire, there was a unique repair....
“Fifteen years ago everybody started specifying shoulders in their cross-section drawings as a unique area of the tire. It used to be crown and sidewall. So the shoulder became an issue. The primary reason is that it is a sensitive area—it is the thickest part of the tire, meaning it is harder to inspect because you have more mass to deal with and it is the transitional part of the tire where you go from the tread stabilization belt area to the very flexible sidewall area.”
“Traditionally, if you had, for example a 1/4-inch nail hole repair in the shoulder of the tire, a '20' (patch size) was used and put over the injury because that's what would be called for on the crown. Unfortunately, it was located where it put one end of that patch body in the high-flex area of the tire.
“And so what could result—it didn't always—but what could result is you could end up with a cord breaking out of the patch because it was flexing at a much higher rate, or you could, in some severe cases, have patch failure at the bottom of the line because it couldn't withstand the shear energy of the flexing. So essentially you had a repair that if the tire came back in, you had to redo the repair.
“So the TRMG group decided that maybe it's time that we start emphasizing again that it's important that you end your patch bodies in non-flex areas,” Mr. Casebere said, adding, “It's not hard, it's just trying to get the discipline back.”
Repair unit manufacturers typically offer templates for calculating placement of a repair patch. But Mr. Casebere said that tire repairers often don't bother using the templates.
“We all make templates that have slots in them that will tell you how much you can shift that patch off-center. The problem is that everybody got lazy and nobody uses templates because most injuries are either crown or sidewall and in some cases shoulder,” he said.
To accommodate this trend, several years ago Rema Tip Top began printing appropriate templates on the bottom of its patch unit boxes that technicians could cut out and use. “So there's no reason for a person to say they don't have a template.”
The RSR recommendations mostly appease customers who didn't want to pay the higher cost of a section repair, according to Gary Tatum, regional sales manager, Patch Rubber Co., which included the RSR procedure on its new wall charts this year.
“It's going to allow dealers to repair smaller injuries in the shoulder of truck tires whereas in the past they had to refer them to retread facilities for section repairs,” noted Kevin Rohlwing, senior vice president of training for the Tire Industry Association (TIA).
The association is incorporating the RSR procedures in its Certified Commercial Tire Service training.
“TIA will be producing a video on (RSR) later this year to show technicians exactly how to do it. You have to offset the repair unit in order to make those repairs work. So we will be working together with TRMG and TRIB (Tire Retread & Repair Information Bureau) to put together an instructional video later this year to teach our certified technicians how to install those repairs properly,” Mr. Rohlwing told Tire Business.
To reach this reporter: [email protected]; 330-865-6127.